Painting a galvanised roof prior to putting solar panels on

Forums › Home Workshop › Painting a galvanised roof prior to putting solar panels on

felixfurtak

11 posts

Geek

Topic # 142764 24-Mar-2014 11:06

Hi,

I'm planning to put solar panels on my roof and since they're going to be up there for a good 15-20 years I think it would be a good idea to paint it beforehand since it would be hard to repair the roof once the solar panels mounted.

The roof in question is an unpainted Galvanized Long Run type. It's in overall fairly good condition, but there are a few small areas that are starting to show a little bit of spot rust.

I think that I need some sort of cold galvanizing paint and have so far looked at the following.

1. Resene Galvo One. $102 / 4L (currently on sale)
2. Dulux Cold Galv. $198 / 4L

Looking at the MSDS sheet for the Galvo One, there doesn't appear to be much zinc in it. I'm guessing the active ingredients are the Barium metaborate (which may have Zinc Oxide in it) or the Alkyd Resin resene.com.au/archspec/msds/Galvo_One.pdf

The Dulux Cold Galv on the other hand appears to be 60% Zinc dust which looks to me to be a whole lot better msds.duluxgroup.com/pdf/shess-en-cds-020-000000010790.pdf

Both are described as primers.

Basically I just want to treat the roof so it doesn't corrode. It's going to have solar panels across the entire roof, so I don't care what it looks like underneath.

Which would work best for me? Also, does it really need a topcoat on top of the 'primer' ?

Any comments of help with this much appreciated.

Felix

ubergeeknz

3343 posts

Uber Geek
+1 received by user: 1089

Trusted

Vocus

Reply # 1011671 24-Mar-2014 11:12

I'd go in there with a wire brush and some rust converter (not remover, which never seems to work well) on the rusty spots, then just prime the whole thing before slapping on a couple coats of paint.

felixfurtak

11 posts

Geek

Reply # 1011711 24-Mar-2014 12:04

Can you recommend any rust converter products? Thanks

mclean

321 posts

Ultimate Geek
+1 received by user: 68

Subscriber

Reply # 1011775 24-Mar-2014 13:24

If you want 20 years more life and it's showing signs of rust you should have a close look at it, especially under the flashings and any other places that don't get washed by the rain. If it's a simple enough roof then a replacement now might be a good investment.

McLean

ubergeeknz

3343 posts

Uber Geek
+1 received by user: 1089

Trusted

Vocus

Reply # 1011790 24-Mar-2014 14:09

felixfurtak: Can you recommend any rust converter products? Thanks

CRC make one. I can't remember which one I used but if I get a chance I'll peek in the shed, that seemed to work well enough.

timmmay

13910 posts

Uber Geek
+1 received by user: 2470

Trusted

Subscriber

Reply # 1011796 24-Mar-2014 14:14

I'd replace any sheets showing any rust, and take a good look at the flashings too. Galv is cheap, roofers aren't too bad, but taking a solar array down sounds problematic and expensive. Paint can't really fix rust, it makes it worse by trapping moisture under where it tissue even faster.

AWS Certified Solution Architect Professional, Sysop Administrator Associate, and Developer Associate
TOGAF certified enterprise architect
Professional photographer

Niel

3267 posts

Uber Geek
+1 received by user: 77

Trusted

Reply # 1011937 24-Mar-2014 16:45

Rust converter must be specific for galvanised iron, else it will cause corrosion - been there done that (on a small scale). And the undercoat needs a top coat, it can't withstand the weather. I'd replace the sheets, or if the budget is really tight and it is out of sight then maybe fit polycarb sheets over it and seal the top edge well - might be hard to match the profile though.

You can never have enough Volvos!

resurrect

80 posts

Master Geek
+1 received by user: 5

Reply # 1011953 24-Mar-2014 17:03

ubergeeknz:
felixfurtak: Can you recommend any rust converter products? Thanks

CRC make one. I can't remember which one I used but if I get a chance I'll peek in the shed, that seemed to work well enough.

I'm pretty sure that repco and super-cheap stock a few different brands and would be an easy enough place to find some.

SepticSceptic

1714 posts

Uber Geek
+1 received by user: 335

Trusted

Reply # 1013847 27-Mar-2014 13:20

ubergeeknz:
felixfurtak: Can you recommend any rust converter products? Thanks

CRC make one. I can't remember which one I used but if I get a chance I'll peek in the shed, that seemed to work well enough.

I have used Black Guard Rust Converter. Works well, and makes a pretty tough over-coating.

I did also try White Knight Rust convertor, but it seemed it wasn't potent enough, and it's dried coat wasn't quite as tough as the Back Guard.

My thoughts are no longer my own and is probably representative of our media-controlled government

mattwnz

13964 posts

Uber Geek
+1 received by user: 1761

Reply # 1013861 27-Mar-2014 13:34

Personally I would replace the sheets under it, as if it is rusting, then it is reaching the end of it's life., and far cheaper to replace those parts now, than after the tube frame has been installed. I'd get a roofer to look at it.